Algeria's state-run news agency says the military operation at the natural gas complex where Islamic militants seized 41 foreign hostages has ended.
But firm information on the fate of the captives is hard to confirm.
The country's communications minister, Mohamed Said, said a "large number of terrorists were neutralized" during the raid. But he also said that several hostages were killed.
A news agency in Mauritania quoted a militant spokesman as saying 34 hostages and 15 kidnappers were killed when Algerian helicopters attacked as the militants tried to move the hostages. That report has not been independently confirmed.
Algeria's news agency reports at least four hostages were freed while others escaped. At least one hostage, an Irishman, has been confirmed safe and has spoken with his family.
Other hostages are believed to include Norwegians, Japanese and Americans.
Al-Qaida-linked militants stormed the Amenas gas complex in eastern Algeria Wednesday for what they say is retaliation for French military operations in Mali. Islamic militants also with ties to al-Qaida are in control of northern Mali and have threatened to move towards the capital.
The gas complex is jointly run by Algerian, British and Norwegian firms. The Pentagon says it is ready to intervene if Algeria asks for help, and a Defense Department official would not deny reports that the U.S. sent a drone over Algeria.
Richard Cochrane, an analyst at London's IHS Jane's security and defense company, says the incident could have long-term economic implications for Algeria.
In an interview with VOA, he said the kidnappings have elevated the risks for foreign investors in the country.
"Algeria is well aware that these sites were targets, which is why guards and the army were on station to respond to these events and the fact that they were unable to defend these workers is going to be a cause of severe embarrassment and perhaps a longer-term problem for Algerians persuading new investors into the country to work in these isolated southern regions," Cochrane said.